The background description provided herein is for the purpose of generally presenting the context of the disclosure. Work of the inventors hereof, to the extent the work is described in this background section, as well as aspects of the description that may not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted as prior art against the present disclosure.
The disclosed technology relates to hard disk drive technology, and more particularly, to calibrating read and write operations in a two dimensional magnetic recording (TDMR) system.
Demand for storage capacity is increasing and motivates the development of hard disk drive systems that can support higher storage capacity by increasing the recording density of the recording medium. However, in practical implementations, an increased recording density may present several design challenges. For example, the increased recording density may necessitate a reduced spacing between adjacent tracks of a hard disk. This may, in turn, cause a larger amount of cross-track interference that complicates the recording and retrieval of data as well as maintaining the data's integrity while stored.
TDMR has been considered as a technique for alleviating the increased level of cross-track interference introduced by increased recording density. While conventional hard disk drive systems employ a single read head for retrieving data from the disk, TDMR systems use multiple read heads that may be configured to concurrently retrieve data from the disk. For example, a simple case of a multi-read head TDMR system may consist of two read heads. The two read heads may retrieve data from adjacent tracks of the hard disk. Compared to the use of a single read head, the concurrent use of two read heads not only enables the retrieval of larger amounts of data per time unit, but also allows the cancellation of cross-track interference. By concurrently retrieving signals from two adjacent tracks, the cross-track interference caused by one of the tracks on the other track may be estimated and cancelled as part of the decoding process. Therefore, as cross-track interference can be a key limitation in hard disk drive systems, the use of TDMR has the potential to significantly improve hard disk drive performance and capacity. However, the use of TDMR in practical implementations faces several design challenges and requires enhanced calibration procedures to coordinate the concurrent access to the recording medium.